Although the n-colour printing process increases the colour gamut, it presents a challenge in generating colour separations. This paper evaluates different methods of implementing the inverse printer model to obtain the colour separation for n-colour printing processes. The constrained optimisation and the look-up table based inversion methods were evaluated. The colorant space was divided into sectors of 4-inks and the inverse printer models were applied to each sector. The results were found to be adequate with the mean CIEDE2000 values between the original colours and the model predicted colours below 1.5 for most of the models. The lookup table based inversion was computationally faster than the constrained optimisation approach. The 9-level lookup table model gave accurate prediction without costing the processing time. It can be used to replace spot coloured inks with the 7-colour printing process in packaging printing to achieve significant cost savings.